Anomalous Stabilization of Hydrodynamic Instability Due to Nonlocal Energy Transport

抑制流体动力不稳定性对发展惯性聚变能至关重要。在开始本研究项目之前，我们发现观测到的瑞利-泰勒不稳定性的增长率小于理论预测，这归因于非局域电子能量输运。尽管抑制增长率本身对激光聚变来说是“好消息”，但尚不清楚在未来的反应堆等离子体中是否会出现同样的效果。本研究的目的是为了更好地理解这个问题。为此，我们进行了以下三个实验。生长速率的抑制在短波长区域最为明显。我们应用了创新的云纹干涉测量法，成功地观察了短波长的不稳定性。增长率与考虑了非定域电子输运的预测相吻合。非局部能量输运的直接证据至关重要。我们发展了x射线半影成像和菲涅耳相位带板成像，并成功地测量了等离子体密度。观测到的密度分布与非局部输运的预测吻合较好。未来反应堆目标的稳定性必须进行测试。我们开发了一种新的激光系统，将现有的所有激光束结合在一起，从而可以模拟未来目标的一小部分，并测量瑞利-泰勒不稳定性的增长率。我们测量所有必要的量来检验各种瑞利-泰勒不稳定理论的活动正在取得成果。尽管存在一些尚未解决的现象，但对于在超过25年的时间里一直是核心问题的消融瑞利-泰勒不稳定性的理解，正接近“游戏的终点”。

Suppression of hydrodynamic instability is critically important for the development of, inertial fusion energy. Before starting this research project, we found that the observed growth rates of the Rayleigh-Taylor instability were smaller than the theoretical predictions, and attributed to the nonlocal electron energy transport.Although the suppression of the growth rate itself is "good news" for laser fusion, it is unclear whether the same effect will be revealed in future reactor plasmas. The purpose of this research is to obtain good understanding to answer this question.For this purpose, we have performed the following three experiments.1. The suppression of growth rates is most pronounced in the short wavelength region. We have applied the innovated moire interferometry, and succeeded to observe the instability at short wavelengths. The growth rates have agreed well with the prediction that takes into account nonlocal electron transport.2. Direct evidence of nonlocal energy transport is critical. We have developed x-ray penumbral imaging and Fresnel phase zone plate imaging, and succeeded to measure plasma density. The observed density profiles were in better agreement with the prediction of nonlocal transport.3. Stability of targets for future reactors must be tested. We have developed a new laser system that combines all the existing laser beams so that a small portion of future target can be simulated, and measured the growth rates of Rayleigh-Taylor instability.Our activity to measure all necessary quantities to test various Rayleigh-Taylor instability theories are bearing fruit. Although there are some unresolved phenomena, the understanding of the ablative Rayleigh-Taylor instability that have been a central issue in more than a quarter century is approaching to "the end of the game".